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Linked specimens: USNM-419241 USNM-419238 USNM-419239 USNM-419240
Extra details from original publication
C fusiformis comprises the entire foraminiferal assemblages in Sample KBJ 8-3 (more than 300 specimens).
Age: Zone P22 (Blow, 1969) of late Oligocene. Although C. fusiformis was not found with other age diagnostic taxa at its type locality, additional specimens of this species were collected from the upper San Hilario section of the San Gregorio Formation located 7.3 km northeast of the type locality (Kim, 1987). Among the additional 12 specimens of this species, 11 are obtained from Sample SH-6 together with Globigerinita glutinata whose range is P22 to Recent (Kennett and Srinivasan, 1983) and one from Sample SH-7 located approximately 25 cm below Sample SH-6. Sample SH-7 represents the lower boundary of the P22 Zone of the San Hilario section based on the first occurrence of G. glutinata and cooccurrence of typical constituents of the P22 Zone assemblage including Globigerina angulisuturalis, G. angustiumbilicata, G. ciperoensis, G. praebulloides, and Globoquadrina venezuelana etc. (Kim, 1987). Sample SH-7 is approximately 3.3 m below the white tuff bed, dated by Hausback (1984) as 25.5 ± 0.4 Ma.
Evolutionary position: Chiloguembelina fusiformis appears to be the descendant of C. victoriana. Comparing the younger Oligocene form and the older Eocene form of C. victoriana of Beckmann's (1957) original figures, several evolutionary patterns can be recognized, i.e. aperture elongating and last chamber thinning in addition to Beckmann's (1957) note on becoming stout. The same evolutionary trends continue from early Oligocene C. victorina through to late Oligocene C. fusiformis.
The shape and position of aperture has been one of the most important bases for grouping species of Chiloguembelina (Beckmann, 1957; Samanta, 1969; Resig and Kroopnick, 1983; Poore and Gosnell, 1985). Considering apertural forms of Oligocene species of this genus, two kinds of divergence trends can be recognized from high and wide apertural shape of Paleocene C. midwayensis midwayensis (Fig. 2). C. fusiformis and C. victoriana represent a trend in which the height to width ratio of aperture increases whereas C. cubensis represents the contrary trend.
Chiloguembelina fusiformis is one of the youngest species of this genus reported yet.
Paleoecology: Chiloguembelina fusiformis occurs together with tropical to warm subtropical species such as Catapsydrax dissimilis and Globoquadrina venezuelana which are abundant in samples SH-6 and SH-7 of the San Hilario section of the San Gregorio Formation (Kim, 1987). Thus, it is assumed that C. fusiformis preferred a warm subtropical setting.
Beckmann, J. P. (1957). Chiloguembelina Loeblich and Tappan and related foraminifera from the Lower Tertiay of Trinidad, B.W.I. In, Loeblich, A. R. , Jr., Tappan, H., Beckmann, J. P., Bolli, H. M., Montanaro Gallitelli & E. Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin . 215: 83-95. gs V O Kim, W. H. (1987). Chiloguembelina fusiformis n. sp. and its paleontological significance. Journal of the Paleontological Society of Korea. 3: 71-77. gs
Beckmann, J. P. (1957). Chiloguembelina Loeblich and Tappan and related foraminifera from the Lower Tertiay of Trinidad, B.W.I. In, Loeblich, A. R. , Jr., Tappan, H., Beckmann, J. P., Bolli, H. M., Montanaro Gallitelli & E. Troelsen, J. C. (eds) Studies in Foraminifera. U.S. National Museum Bulletin . 215: 83-95. gs V O
Kim, W. H. (1987). Chiloguembelina fusiformis n. sp. and its paleontological significance. Journal of the Paleontological Society of Korea. 3: 71-77. gs
Chiloguembelina fusiformis compiled by the pforams@mikrotax project team viewed: 30-11-2022
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